I was changin DS2's diaper and noticed a yellowish "bump" under the skin on his penis. Please forgive my terminology, I have no idea what I'm talking about and I'm freaking out.

Its not right at the opening, its a bit off to the side, but fairly close to the tip. Its not real large, but bigger than a regular pimple. But, it looks like a really large pimple. I touched it and kind of moves a bit, but I don't want to mess with it to find out more.

No need to freak out. This is probably what is called a smegma pearl, a normal and non pathological variation in the development of the foreskin.

As the foreskin starts to separate from the head of the penis, cells that had attached the two are shed, and can accumulate in pockets underneath the foreskin. These shed cells are called smegma. This accumulation can look like a lump under the foreskin. As separation proceeds, a path to the opening of the foreskin will eventually develop and the accumulated cells will work their way to the opening and discharged as crumbs or a lump of usually whitish, odorless, pasty-dry material.

You do not have to do anything with a smegma pearl. No need to try to manipulate it. It will take care of itself in time. Just know that in some cases it can take a number of years until the trapped cells find their way out, or it may take less. The foreskin can look pretty lopsided in the meantime. But its totally fine and normal. Welcome to the normal foreskin club!

very man has a question about there sexual health at least once in their life and one of the biggest topics are about bumps or brown spots on their penis. These spots are often normal in men, easily treatable, or sometimes a sexually transmitted disease.

One of the most common bumps found in men are called penis papules. They are very common, effecting up to 80% of men starting from before the age of ten all the way into adulthood. They are small often white bumps usually found at the base of of the shaft.

Boils are common as well and are often mistaken for genital herpes because of there similar appearence bit are often not dangerous and will go away on there own.

Brown spots can be normal as well if they are not raised but should be looked at because of the possability of penile cancer.